He accepted an earldom in 1796 from Portland's successor William Pitt the Younger, rather than the reported previous offer of a marquessate; in the absence of there being another dukedom in keeping with Grey family tradition (cf Henry Grey, 1st Duke of Suffolk), Stamford deemed it better to preserve the memory of his grandmother's whose estates he had inherited.

Thus he received the additional titles of Baron Delamer and Earl of Warrington (in the peerage of Great Britain) in recognition of the Booth family.

Stamford modernised the family's Staffordshire seat at Enville Hall to the design of Thomas Hope.

He promoted the development of the town of Ashton-under-Lyne (where he had appointed his cousin, George Booth as Rector) near Manchester, on land inherited from the Earls of Warrington.

On 28 May 1763, Grey married Lady Henrietta, second daughter of William Bentinck, 2nd Duke of Portland and the art collector Margaret Bentinck, Duchess of Portland, only daughter and heiress of Edward Harley, 2nd Earl of Oxford and Earl Mortimer at Stamford House, Whitehall, and registry office, Westminster, having nine children including:[1][5] On his death in 1819 at Enville Hall, he was succeeded by his eldest son.